Age and sex effects on corpus callosum morphology across the lifespan.

The corpus callosum (CC) is the largest interhemispheric white matter tract in the human brain, and is characterized by pronounced differences in morphology among individuals. There are limited data, however, regarding typical development, sex differences, and the neuropsychological correlates of individual differences within CC subregions. Magnetic resonance (MR) imaging exams were collected in a large cohort (N = 305) of healthy individuals (ages 8-68). We used a highly reliable program to automatically identify the midsagittal plane and obtain CC subregion measures according to approaches described by Witelson [1989]: Brain 112:799-835 and Hampel et al. [1998]: Arch Neurol 55:193-198 and a measure of whole CC shape (i.e., circularity). CC measurement parameters, including area, perimeter, length, circularity, and CC subregion area values were generally characterized by inverted U-shaped curves across the observed age range. Peak values for CC subregions were observed between ages 32 and 45, and descriptive linear correlations were consistent with sharper area changes in development. We also observed differing age-associated changes across the lifespan between males and females in the CC subregion corresponding to the genu (Witelson's subregion 2), as well as CC circularity. Mediation analysis using path modeling indicated that genu area mediated the relationship between age and processing speed for females, and the relationship between age and visual learning and executive functioning for males. Taken together, our findings implicate sex differences in CC morphology across the lifespan that are localized to the genu, which appear to mediate neuropsychological functions.

Financial hardship and risk of suicide among U.S. Army personnel.

Financial stress has been frequently identified as a risk factor for suicidal behavior, both in military and civilian groups. However, it remains unclear to what degree financial stress may be associated independently with suicide behavior when accounting for other risk factors. This study examined data on suicide and suicide attempt cases in the Department of Defense Suicide Event Report compared with service members who did not have recent suicide behavior. The resulting multinomial regression analysis found that financial distress had a weak association with suicide, and its relationship to suicide attempts was not statistically significant. Compared with financial distress, relationship problems and substance abuse history appeared to have much stronger associations with suicidal behavior, as did having a diagnosis of a mood disorder, such as major depressive disorder. The major conclusion from these data are that although financial distress may be a risk factor for suicidal behavior, the relationship is likely indirect and considerably less substantial than previously suspected. In addition, its relative influence is significantly less than other identified risk factors. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Age-related differences in white matter tract microstructure are associated with cognitive performance from childhood to adulthood.

BACKGROUND: Age-related differences in white matter tract microstructure have been well established across the life span. In the present cross-sectional study, we examined whether these differences are associated with neurocognitive performance from childhood to late adulthood. METHODS: Diffusion tensor imaging was performed in 296 healthy subjects aged 8 to 68 years (mean = 29.6, SD = 14.6). The corpus callosum, two projection tracts, and five association tracts were traced using probabilistic tractography. A neurocognitive test battery was used to assess speed of processing, attention, spatial working memory, verbal functioning, visual learning, and executive functioning. Linear mediation models were used to examine whether differences in white matter tract fractional anisotropy (FA) were associated with neurocognitive performance, independent of the effect of age. RESULTS: From childhood to early adulthood, higher FA of the cingulum bundle and inferior frontooccipital fasciculus (IFOF) was associated with higher executive functioning and global cognitive functioning, respectively, independent of the effect of age. When adjusting for speed of processing, FA of the IFOF was no longer associated with performance in the other cognitive domains with the exception of visual learning. From early adulthood to late adulthood, white matter tract FA was not associated with cognitive performance independent of the age effect. CONCLUSIONS: The cingulum bundle may play a critical role in protracted maturation of executive functioning. The IFOF may play a key role in maturation of visual learning and may act as a central "hub" in global cognitive maturation by subserving maturation of processing speed.